The present inventor previously searched for an enzyme capable of efficiently hydrolyze 3.alpha.-sulfuric acid esters of sulfated bile acids for the purpose of enabling enzymatic assay of sulfated bile acids in blood or urine. As a result, it was found that the bacterial species Pseudomonas testosteroni, which belongs to the genus Pseuomonas, produces the desired enzyme, bile acid sulfate sulfatase. The bile acid sulfate sulfatase produced by said bacterial species is characterized in that it acts on 3.alpha.-sulfated bile acids, leading to the formation of 3.beta.-hydroxy bile acids. Therefore, it was made possible to assay 3.alpha.-sulfated bile acids by oxidizing said 3.beta.-hydroxy bile acids to 3-oxobile acids under the action of .beta.-hydroxysteroid dehydrogenase in the presence of .beta.-NAD, which is a coenzyme for said dehydrogenase, with simultaneous reduction of .beta.-NAD to NADH, and assaying the thus-formed NADH by a per se known method (cf. Japanese Unexamined Patent Publication No. 02-145,183).
However, such a method of producing bile acid sulfate sulfatase as mentioned above has drawbacks. Thus, it is an indispensable condition that cholic acid or the like, which is expensive, should be added, as an inducer substrate, to the medium. Moreover, the yield of bile acid sulfate sulfatase is low and the production procedure is rather complicated.
Accordingly, it is an object of the present invention to provide a method of producing 3.alpha.-bile acid sulfate sulfatase in high yields and at a low cost in an easy and simple manner.